Human herpesvirus 8 (HHV-8): HHV-8 DNA sequences were found in spindle cells, rather than stromal areas, of Kaposi's sarcoma (KS), supporting the role of this virus in the pathogenesis of KS. Intensive efforts were made to develop and evaluate techniques to detect HHV-8 antibodies and genome in peripheral blood. An immunofluorescence assay with high specificity and moderate sensitivity showed a higher HHV-8 seroprevalence among women of Haitian than American origin. Detection of antibodies against HHV-8 peptides has been inconsistent, but detection of HHV-8 DNA has shown promise and is being actively pursued. Human Papillomaviruses (HPV): The development and application of assays for HPV antibodies is a major effort. Antibodies to HPV 16 virus-like particles had good interlaboratory concordance in a multicenter study, and antibodies against several HPV peptides were shown to be elevated in women with cervical neoplasia. Seroepidemiologic evidence also supported the relation of HPV with non-cervical anogenital tract cancers, although prostate cancer was not associated with HPV DNA or antibodies. Studies have been started to investigate cell-mediated as well as humoral immunity in persistent HPV infection and development of disease, both with and without HIV co-infection. Polyomaviruses: Exposure to live simian virus 40 (SV40) through contaminated poliovirus vaccines widely distributed between 1955 and 1963 did not increase the risk of cancers purported to contain SV40 DNA, based on analysis of U.S. cancer incidence and mortality data and an extensive review of previous epidemiologic studies. SV40 DNA was not detected in urine samples of immune compromised HIV infected homosexual men. However, the human polyomaviruses, JC and BK viruses, were prevalent in these samples, confirming that human polyomaviruses but not SV40 are common human infections. The possibility that JC virus may be associated with childhood acute lymphoblastic leukemia is being evaluated. Hepatitis Viruses: The newly discovered hepatitis G virus RNA in plasma was unrelated to HIV-co-infection and also unrelated to hepatic failure among subjects in the Multicenter Hemophilia Cohort Study.